math
posted by lisa .
the class is 50 students 30 like chocolate, 25 like vanilla, and 18 like both, which like neither.

If 18 like both, then (3018) like just chocolate and (2518) like vanilla.
50  18  12  7 = ? 
18Ã·2=9
309=21
259=16
16+21=37
5037=13